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Sunday, January 8, 2023

on video B727 Brakes


 Normal Operation. Self adjusting, multidisc hydraulic brakes with incorporated brake wear indicators are installed at each main gear wheel. They are operated by the pilots brake pedals or the pneumatic brake handle (main gear only). An anti skid system is installed to maximize normal braking capability and prevent locked wheels. Pressure sources are available from hydraulic system "B", "A", brake accumulator and pneumatic pressure source, nose brake power is from system "A" (if installed). As previously mentioned system "A" may power the brakes via the brake interconnect valve. Check valves retain pressure in the brake system if hydraulic pressure is  lost. A fully charged brake accumulator stores enough fluid under pressure for several brake applications.

There are bake pressure gauges in the cockpit and left hand wheel well this will show hydraulic pressure and accumulator air pressure. Normal operating pressure is 3000 psi. Pressure surges trapped by the check valve may cause indications to rise to 3500 psi. When all the fluid pressure is depleted from the accumulator the indicator will read pecharge pressure, about 1000 psi.

Pilot control of the braking is through the brake pedals to the brake metering valves, one for each main gear. Stepping on the brake pedals actuates the respective metering valve. As the metering valve moves a proportional amount of hydraulic pressure is directed to the anti skid valves and lock out deboosters, then to the wheel brakes. The deboosters reduce hydraulic pressure and isolate the fluid downstream. Thus if a leak occurs between the debooster and the brake, only the isolated fluid is lost. and you won't have a system "B" hydraulic loss. A servicing handle on the debooster replenishes the isolated fluid (part of pre flight).


 Normal Operation. Self adjusting, multidisc hydraulic brakes with incorporated brake wear indicators are installed at each main gear wheel. They are operated by the pilots brake pedals or the pneumatic brake handle (main gear only). An anti skid system is installed to maximize normal braking capability and prevent locked wheels. Pressure sources are available from hydraulic system "B", "A", brake accumulator and pneumatic pressure source, nose brake power is from system "A" (if installed). As previously mentioned system "A" may power the brakes via the brake interconnect valve. Check valves retain pressure in the brake system if hydraulic pressure is  lost. A fully charged brake accumulator stores enough fluid under pressure for several brake applications.

There are bake pressure gauges in the cockpit and left hand wheel well this will show hydraulic pressure and accumulator air pressure. Normal operating pressure is 3000 psi. Pressure surges trapped by the check valve may cause indications to rise to 3500 psi. When all the fluid pressure is depleted from the accumulator the indicator will read pecharge pressure, about 1000 psi.

Pilot control of the braking is through the brake pedals to the brake metering valves, one for each main gear. Stepping on the brake pedals actuates the respective metering valve. As the metering valve moves a proportional amount of hydraulic pressure is directed to the anti skid valves and lock out deboosters, then to the wheel brakes. The deboosters reduce hydraulic pressure and isolate the fluid downstream. Thus if a leak occurs between the debooster and the brake, only the isolated fluid is lost. and you won't have a system "B" hydraulic loss. A servicing handle on the debooster replenishes the isolated fluid (part of pre flight).

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